Friday, March 7, 2014

Power drills have replaced hand drills
and hand braces in timber work because they are faster and easy to operate.
Power drills are operated either by electricity (Electric drills) or by
compressed air (pneumatic drills).

There are two types of power drills, the
heavy duty type and the light duty type. Figure A below shows the heavy duty
type and Figure B shows the light duty type.

Normal
power drills rotate the drill bit fixed to it at very high speed and make drill
holes of required size. In some drills the speed is adjustable according to the
cutting material.

Twist
drill bits, usually made of High Speed Steel (HSS) are used in drilling wood,
steel and other soft metals. Drill bits are available from 1mm diameter to 25mm
or more with 0.5mm steps. For portable power drills the maximum drill size is
10 or 12mm.

HSS
drill bits are not suitable for drilling masonry. The type of drill bit used
for masonry are carbide tipped bits which are used with hammer drills, which
have a percussion effect in addition to rotation.

For
electrical safety it is best to use power tools rated at 110 volts. Since the
normal power supply is 230 volts, a step down transformer 230/110 volt should
be used with power tools. For more safety battery operated power drills are now
available. Figure below shows a battery operated power drill.

Power drills with variable speeds can
also be used as screw drivers to drive and remove screws.

SANDERS.

Sanders or sanding machines are power
tools used to smooth finished frames and wood items. Sanders have the means to attach sand paper
and to move it rapidly over the wood. These may be powered by electricity or
compressed air. There are three types of sanders.

Orbital
sanders – In the orbital sander the disk with the sanding pad rotates while
moving in an orbital path. This ensures that the sanding material does not
travel the same path twice thus ensuring that there are no swirl marks.

2.Belt sander
is a machine which consists of an electrical motor that turns a pair of drums
on which a seamless loop of sandpaper is mounted. Belt sanders can be either
hand-held, where the sander is moved over the material, or stationary (fixed),
where the material is moved to the sanding belt. Stationary belt sanders are
sometimes mounted on a workbench, in which case they are called bench sanders.

Belt Sander

Belt Sander – upside down

The Disk Sander

The Disk Sander is fixed to a work bench and the material to be smoothed is moved over the sanding surface. Disk sanders are dangused to smooth materials such as woods and plastics. It is also used to remove small amounts of waste material. It is a dangerous machine if serous machines and goggles, hand and finger protection must be worn when using

Cleaning and storing portable power
tools.

Power tools should be well maintained to
give better service and long life. Maintenance of power tools include:

1.Cleaning
after use – Brush or wipe off dust and cut material, lubricate moving parts,
clean and check electrical contacts.

2.Cable
care – Check power cable for any damages or loose connections. Promptly replace
if damaged. Fold the cable back to position.

Store – Store
securely in its proper location with due regard to tool safety and user safety